Payments

import { createPaymentClient } from "@a3stack/payments";
import { privateKeyToAccount } from "viem/accounts";

const account = privateKeyToAccount(process.env.PRIVATE_KEY);

const payer = createPaymentClient({
  account,
  chains: ["eip155:8453"],  // supported chains (Base default)
  // maxAmount: "1000000",  // optional: max USDC to auto-pay (safety cap)
});

// Auto-pays x402 requirements transparently
const response = await payer.fetch("https://api.paidagent.ai/tool");
const data = await response.json();

// Or target a specific agent by ERC-8004 ID
// (auto-resolves payment wallet from on-chain registration)
const paidFetch = await payer.fetchForAgent("eip155:8453:0x8004...#2376");
const response = await paidFetch("https://mcp.paidagent.ai/tool");

// Check your USDC balance on Base
const balance = await payer.getBalance("eip155:8453");
// {
//   amount: 1500000n,      // raw USDC (6 decimals)
//   formatted: "1.500000", // human-readable
//   symbol: "USDC",
// }

// After a paid request, decode the payment receipt
const receipt = payer.decodeReceipt(response);
// {
//   txHash?: "0x...",
//   from: "0x...",
//   to: "0x...",
//   amount: "1000",
//   asset: "0x833589...", // USDC
//   chain: "eip155:8453",
//   timestamp: 1733000000,
// }

// Check if an endpoint requires payment before connecting
const check = await payer.checkPaymentRequirements("https://api.agent.ai/tool");
// {
//   requiresPayment: true,
//   amount: "1000",
//   asset: "0x833589...",
//   network: "eip155:8453",
//   payTo: "0x1be93C..."
// }

import { createPaymentServer } from "@a3stack/payments";
import { USDC_BASE } from "@a3stack/payments";

const receiver = createPaymentServer({
  payTo: "0x1be93C...",     // your wallet — receives USDC
  amount: "100000",          // 0.10 USDC in base units (6 decimals)
  asset: USDC_BASE,          // USDC address on Base
  chain: "eip155:8453",
  description: "My AI tool, 0.10 USDC per call",
  // facilitator?: "https://...",  // optional custom facilitator URL
});

import express from "express";
const app = express();

app.use("/tool", receiver.middleware(), (req, res) => {
  // ✓ Payment verified at this point
  const payment = res.locals.payment; // PaymentDetails

  console.log(`Received ${payment.amount} USDC from ${payment.from}`);

  res.json({ result: "premium content" });
});

app.listen(3000);

// Manual: check if a request carries valid payment
const { valid, payment, error } = await receiver.verify(req);
if (!valid) {
  const reqs = receiver.buildRequirements("https://api.myagent.ai/tool");
  res.status(402).set("X-PAYMENT-REQUIRED", reqs).end();
  return;
}

// Payment valid — serve the response

import { PaymentClient } from "@a3stack/payments";

// Direct class instantiation (same as createPaymentClient)
const client = new PaymentClient({ account });
const balance = await client.getBalance("eip155:8453");

import { USDC_BASE, USDC_ETHEREUM, USDC_ARBITRUM } from "@a3stack/payments";

// Base mainnet USDC
console.log(USDC_BASE);
// "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"

// The x402 payment flow in detail:

// 1. Client makes a normal HTTP request
GET /tool HTTP/1.1

// 2. Server returns 402 with payment requirements
HTTP/1.1 402 Payment Required
X-PAYMENT-REQUIRED: { "accepts": [{ "scheme": "exact", "network": "eip155:8453", ... }] }

// 3. Client signs EIP-3009 authorization (gasless — no ETH needed, just USDC)
// Authorization: Transfer USDC from client to agent's payTo address

// 4. Client retries with X-PAYMENT header
GET /tool HTTP/1.1
X-PAYMENT: <base64-encoded EIP-3009 signature>

// 5. Server verifies signature and responds
HTTP/1.1 200 OK
X-PAYMENT-RESPONSE: { "success": true, "txHash": "..." }

// 6. Facilitator settles the USDC transfer on-chain
// Client: -0.001 USDC   Agent: +0.001 USDC